1. Field of the Invention
The present invention relates to a photosensitive polymer composition, to a method of using the composition for forming relief patterns, and to electronic parts. More precisely, it relates to a positive tone, heat-resistant photosensitive polymer composition capable of being converted into a heat-resistant polyimide polymer under heat, which is suitable for passivating films, interlayer insulating films and others for electronic parts such as semiconductor devices, etc.; to a method of using the composition for forming relief patterns; and to electronic parts.
2. Description of the Related Art
Polyimides have good heat resistance and good mechanical properties, and are readily formed into films of which the surface could be well planarized. Having those advantages, they are widely used for passivating films, interlayer insulating films and others for semiconductor devices.
Where polyimides are used for passivating films or interlayer insulating films, the step of forming through-holes and the like in those films is achieved essentially in an etching process in which a positive tone photo-resist is used. However, the step comprises applying and removing such a photo-resist, by which the step is complicated. This is the problem with the step. For the purpose of rationalizing the working step, heat-resistant materials with photosensitivity have heretofore been studied.
Relative to photosensitive polyimide compositions, for example, known are (1) a polyimide precursor composition in which is introduced a photosensitive group through ester bonding (JP-B 52-30207, etc.), and (2) a composition as prepared by adding a compound that contains a carbon-carbon double bond capable of being dimerized or polymerized by the action of chemical rays, an amino group and an aromatic bisazide, to a polyamidic acid (JP-B 3-36861, etc.).
In use of such photosensitive polyimide compositions, in general, a solution of the composition is applied onto a substrate, then dried, and exposed to active rays via a mask, and thereafter the unexposed area is removed with a developer to form a pattern on the substrate.
However, the compositions (1) and (2) noted above are both negative tone ones, and the development for these requires an organic solvent. Therefore, when an etching process using a positive tone photo-resist is switched to a process using a negative tone photosensitive polyimide, the problem is that the mask for the exposure device and the development equipment must be changed.
On the other hand, relative to positive tone photosensitive polyimides, for example, known are (3) a polyimide precursor in which is introduced an o-nitrobenzyl group through ester bonding (JP-A 60-37550), and (4) a composition comprising a phenolic hydroxyl group-having plyamidate and an o-quinonediazide compound (JP-A 4-204945).
However, the precursor (3) is essentially sensitive to light having a wavelength of not longer than 300 nm, and its sensitivity is low. Therefore, the precursor (3) is problematic in that an i-line stepper (for single wavelength light of 365 nm) which is much used these days in the art is hardly applicable thereto. On the other hand, the composition (4) is also problematic in that its sensitivity is still unsatisfactory even though higher than the sensitivity of the precursor (3). At present, no one could obtain positive tone photosensitive polyimides having satisfactorily good sensitivity.